This week I saw a very young puppy, Bobby, die in the most unpleasant way after succumbing to suspected parvovirus infection. It was a reminder, if one was needed, of the importance of vaccinating dogs.

Parvovirus is just one of the illnesses which can be prevented almost completely by giving a course of vaccinations to all puppies at the right age, followed by an annual booster vaccination.

When this illness first occurred in dogs in the UK in the 1970s, I was a veterinary student spending my holidays in veterinary practices. There was an epidemic of parvovirus and many dogs died, especially puppies. As it was a genuinely new disease, probably a mutation of an existing virus, dogs had no immunity to it until a vaccine was developed. The main symptoms are severe diarrhoea with blood and vomiting, leading quickly to lethargy, dehydration and death. In young pups the virus can also affect the heart muscle, and this is another reason for the high death rate. There is no specific treatment for the virus itself so supportive measures like intravenous fluids, pain relief and intensive nursing are given, along with other drugs like antibiotics for secondary bacterial infection. No-one involved in trying to treat these cases will forget the suffering or the awful and characteristic smell associated with it. Some did survive, but most didn’t.

Vaccination has now been given routinely for three decades, so the level of immunity in the dog population of the UK is much better, but we do still see too many cases in susceptible dogs.

When a bitch has a litter of puppies, she passes on immunity to the puppies in two main ways: via the placental blood and via the milk. The antibodies the puppy receives will protect it for the first few weeks of life, but as the levels fall with time they need to be increased by vaccination. Unfortunately if the vaccination is given too early, the response will not be good because the antibodies from the mother interfere with it. If the vaccination is given too late, the puppy will be left vulnerable to infection in between having immunity from its mother and immunity from its vaccination. This is why vets recommend vaccinating within a fairly narrow age range which research has shown will give maximum benefits. Typically this would be between 2 and 3 months of age.

The various component parts of the dog vaccination last for different lengths of time, so some parts will require a booster every year, some every two years and some every three years. So although your vet recommends an annual booster, it may not be against every disease every time. Parvovirus may not need to be given every year, but it depends on exactly which vaccine is given.

Vaccination regimes can seem complicated and some people worry about possible over-vaccination. The best way to understand what is being recommended is to ask your vet what they are advising, and why. Don’t be afraid to ask so that you understand what is being given to your dog. There are of course some risks involved in vaccination itself, but these are outweighed many, many times over by the risks of not vaccinating.

My puppy patient this week was very unlucky. His owner acquired him from a reputable source and intended to have him vaccinated at the right age, but before he could do so he was exposed to the infection when at his most vulnerable. Although he had not mixed directly with other dogs, the infection could have been brought in on a visitor’s hands or shoes. The virus is highly contagious and survives on inanimate objects for weeks or months.

Sadly, Bobby died just a few days after moving to his new home, just when his new owner was starting to get to know him.There are many other causes of diarrhoea and vomiting. If you your dog has diarrhoea or vomiting, please contact your vet or use our interactive Dog Symptom Guide to help you decide what to do next.